I down loaded webroot on my computer it told me to shut down my computer & restart it.it would not boot up?

I bought a new web root virus protection for my computer.When I down loaded it it told me to shut my computer down and then re boot it. When I did this the black screen came on running through the programs. Than the screen went completely black.I did everything I could think of and nothing happen.I final left it on and the blue screen came on with icons.It starting to run programs but it is taking for ever.What happen when I download the web root. I un installed the old virus I had that was running out and down loaded new web root.I have windows on my computer. could you please tell me what I need to do to get my computer running again with this new web root virus.